This invention relates to a test cable arrangement such as is used in the determination of electrophysiological parameters, for example in electrotherapy and electrodiagnostics.
In the implantation of heart pacemakers, defibrillators, neurostimulators and similar implants or in electrophysiological examination, the necessary electrodes or probes are usually initially introduced into the vascular system. As described in U.S. Pat. No. 4,141,367, issued Feb. 27, 1979 to L. A. Ferreira for a Cardiac Electrode/Pacer System Analyer, with the help of a suitable test cable, a connection is made between the sterile probe on the one hand and, on the other, the test instrument, which is located in the nonsterile zone. A sterile test cable arrangement is used for this purpose.
The resterilizable test cable used in this case is massively constructed and fitted with sturdy terminals. Their weight is correspondingly heavy and their flexibility correspondingly slight. These properties mean that the test cable cannot remain hooked up during the manipulation of the probe. Further, it is difficult to attach the alligator clips to the small plug of the probe in such a way that an adequately reliable connection is made without electrical contact errors occurring.
After the measurements have been performed, the measurement cable is then cleaned, dried, inspected for electrical and mechanical integrity, packaged, and finally subjected to sterilization. Aside from the logistical problem of having a sterile cable available at the proper time, another problem arises:
Because the cable is commonly inspected by care personnel without appropriate instructions and test apparatus, there is scarcely any assurance of quality control. Cable breaks, defects in insulation, intermittent contacts, or hygienic defects can result.
It is an object of the invention to furnish a test cable arrangement that avoids the stated disadvantages and to design a test cable that provides the needed consistent quality, sterility and continuous availability with simple resources. Good contact with the plug of the sonde must be guaranteed, and the test cable must be easy to use.
At the probe end, that is, in the sterile zone, the test cable has a support element with contact elements arranged thereon, the support element preferably being a paperboard card measuring approximately 6 cmxc3x978 cm. Fastened to this paperboard is a tube-shaped contact spring with a hole into which the contact pin of an electrode plug fabricated in compliance with EN 50077xe2x80x94commonly called an IS-1 plugxe2x80x94is inserted.
In order to guarantee reliable electrical and mechanical contact, the contact spring is equipped with elastic elements or, as in the present case, exhibits a mechanical prestressing of the slotted tube.
The second electrical connection to the IS-1 electrode plug ring required for the measurement procedure in the case of bipolar probes is effected with an alligator clip. Contact spring and alligator clip are each connected to a thin twin-conductor wire, for example LIY (Z) with a wire cross-sectional area of 0.08 mm2 and an outside diameter of 0.9 mm per strand.
In a further advantageous development of the invention, a support element is equipped with a contact terminal with axial access and a clamp terminal, the clamp terminal being arranged in the area of the electrode plug ring.
It is also possible to effect electrical contact with the contact surfaces of the probe not via a contact spring with axial access or an alligator clip, but by inserting the electrode plug on two clamp terminals. Such clamp terminals are known as holders for fine fuses, in which case the fuses are pressed into the clamp terminals. Arbitrary combinations of clamp terminals, contact springs and alligator clips are conceivable for the contacting of the probe connections.
The support element further has, on at least one external edge, guiding grooves or notches, which prevent the wire slipping off when it is wrapped around the support element in the storage or shipping condition.
At an appropriate place, the contact spring is soldered or otherwise electrically effectively connected, for example by crimping, to one strand of the wire. The other strand of the twin-conductor wire is electrically connected to the alligator clip or clamp terminal.
By way of tension relief, the twin-conductor wire, either as individual strands or as the whole, is passed through cutouts in the support element.
The length of the free strand of the twin-conductor wire connected to the alligator clip is a few centimeters longer than that of the strand connected to the contact spring. In this way, the alligator clip has enough room to move for clamping to the IS-1 connection.
If the probe system to be tested is a so-called unipolar configuration, the alligator clip is simply pulled off the support element, the free length of this wire strand is extended by separating the twin connection to the requisite length, and the alligator clip is brought into electrical contact with the tissue in known fashion.
The support element is made of a material, for example paperboard, the nature of which is such that it can be used only once. Cleaning by washing followed by resterilization is not possible with paperboard or cardboard. In this way, the entire test cable cannot be reused, and thus a new, quality-controlled test cable system must be employed for each measurement procedure.
It is easy to understand that single-use test cables according to the invention are ultimately more economical through mass production if the costs of cleaning, packaging and resterilization of conventional measurement cables as heretofore used, with all their time and personnel expense, are taken into consideration.
The other, proximal end of the electrical line in the form of the twin-conductor wire generally lies in the nonsterile zone and must finally be connected to the test apparatus.
This cable terminal must satisfy the following requirements: reliable electrical contact with the test apparatus and protection of the patient against dangerous voltages or currents.
The following solutions are proposed according to the invention:
The twin-conductor wire is attached to a second proximal support element made of, for example, paperboard, and its electrical conductors are connected to soldering eyes, which are arranged at separate locations, but at the edge of the support element if possible. Also provided for in this case are riveted, cemented, or the insertion connections already described above.
For contacting with the test instrument, the original connecting cable of the test instrument is now used, which cable does not need to be sterile in this case and therefore need not be subjected to the burdensome cleaning/sterilization procedure.
Because these test cables are as a rule equipped with two alligator clips, the rings of the soldering eyes readily suggest themselves as point of attachment.
It would also be conceivable, instead of the soldering eyes at the end of each strand of wire, to bend the stripped wire ends into loops and solder them together. The alligator clips of the measurement cable could then engage in these wire loops. The above-mentioned eyes or wire loops are to prevent the alligator clip from slipping off the wire strand.
Another alternative for the contacting of the wire to the test instrument is simply to separate the conductors of the wire and leave their ends insulated. The necessary electrical contact is achieved only when the ends are inserted into appropriate terminals and contact blades cut through the insulation. Such contactings are common, for example, in the case of RJ11 plugs, the so-called Western plugs from telephone technology.
It is further proposed that a plug connection, for example in the form of an RJ11-4 plug, be arranged at the proximal end of the wire, which preferably has a strand diameter of less than 0.95 mm, which plug connection is inserted into a mating socket of the test instrument or of a connecting cable. In order that test instruments already in service need not be modified, it is proposed that the alligator clips of the original test cable belonging to the test instrument be replaced with a mating socket at the patient end, that is, where the alligator clips are arranged. These RJ11 plug connections, known as Western plugs from telephone technology, have the following advantages: They are economical, are easy to connect to the wire, and have a safeguard against touching. If RJ11-4 plugs are used, they cannot be inserted in telephone jacks because they are designed for the receiver connection.
For better distinction, the twin-conductor wire should have wire strands in unlike colors.
The hole in the support element according to FIG. 2 serves to guide the probe. Specifically, if the probe is first inserted through this electrode hole from below and the IS1 contact pin is then connected to the contact spring, the IS-1 connection is fixed in the axis AA.
Also punched through the proximal support plate is a hole approximately 5 mm in size, which, however, serves in this case to fix in place the support plate, for example with the aid of a fabric clip, in order to prevent its slipping off when the cable of the test instrument is connected.
Another feature is the light weight and great flexibility of the arrangement. In the arrangement according to the invention, the mass of the wires is just roughly of the order of some 3 g/m (twin-conductor wire) for a strand diameter of approximately 0.9 mm. The mass of a 100 cm long test cable arrangement with proximal support element is only some 9 g. Because this thin, light and flexible wire requires the slightest flexural and torsional forces and thus poses scarcely any obstacle, the contactings can be left in place throughout the probe placement procedure.
Because the test cable is fabricated from fine-stranded, light and flexible wire and is made as a disposable part, quality and sterility are permanently assured.
If the wires are soldered to the alligator clips or contact springs and so forth, pointed and sharp edges cannot be prevented from occurring at the solder joints, which edges can under certain circumstances damage an OP glove. It is therefore proposed that adhesive dots made of paper or other material be affixed over the solder joints.
It is also proposed that the solder joints be arranged on the side facing the support element.
It is further proposed that the proximal support element have two electrically isolated contact surfaces, for example in the form of copper coatings on a plastic board, which are electrically connected to the respective wire strands. This contact card, which is about the size of a check card or smaller, is then inserted into a slot in the test instrument or a connected adapter and connects the wires to the test instrument.
If so-called two-chamber pacemakers are used, two electrodes are implanted, one in the atrium and one in the ventricle.
Suitable test instruments then have one connection both for the atrial and for the ventricular electrode. Accordingly, two separate measurement cables are also required.
For this application it is proposed that, for example, a Western plug (also known as an RJ11/RJ12/RJ45 modular plug) be connected to two twin-conductor wires, each of which has at its distal end a support element with the requisite contacting devices according to the configuration already described above and bears appropriate distinguishing features for use on the atrial and ventricular electrode, respectively.
It is further proposed that the contact layout of the modular connecting plug 22 in this case be such that a test cable arrangement according to the invention can be connected to a two-chamber test instrument via connecting socket 23 both for single-chamber application and for two-chamber application.
An arrangement is conceivable in which, for example, the twin-conductor wire for the atrial electrode is connected to contacts 1 and 2, which lie next to each other, and the twin-conductor wire for the ventricular electrode is connected to contacts 3 and 4.
A test cable according to the invention for a single-chamber application in the ventricle would then have only the contact layout 3 and 4.